My read is that perhaps the players who do it have convinced themselves it's actually achieving something besides feeding the enemy. And the more others repeat this, the more validation the "theory" gets.
For what it's worth, it could be a valid choice for a situational tempo tactic, e.g. to throw enemy skirmishers into disarray, kill snipers, trap tanks, etc.
If this fad stays around at least a week longer, i expect players on the receiving end of this "strategy" to get quite good at rapidly converting the donation stream into economy.